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TEHRAN, Iran — A package of incentives that represents a major initiative by world powers to persuade Iran to curb its nuclear program contains "positive steps" but also some "ambiguities," the country's top nuclear negotiator said Tuesday.

Speaking on state television after receiving the proposals from EU foreign policy chief Javier Solana, Ali Larijani called the meeting with Solana "constructive" and said Iran would respond after studying the incentives.

"The proposals contain positive steps and also some ambiguities," Larijani said, adding that more talks were needed.

"We hope we will have negotiations and deliberations again after we have carefully studied the proposals," he said.

The incentives were agreed on by the five veto-wielding members of the U.N. Security Council — the United States, Britain, France, Russia and China, and Germany — at a meeting in Vienna on Friday.

Solana, who arrived in Tehran on Monday night, met Larijani for two hours at the Supreme National Security Council building in central Tehran. Journalists were barred from the building.

'A new relationship'
On his arrival Solana said the European Union and other countries backing the Iran proposal hoped for “a new relationship on the basis of mutual respect and trust.”

“If there is the political will to solve Iran’s nuclear issue without any attempt to politicize it, I think we can come to a comprehensive agreement,” said Iranian Foreign Minister Manouchehr Mottaki.

Iran says its nuclear development is for peaceful production of nuclear energy, but Washington, the European Union and others accuse Tehran of covertly trying to build a nuclear arsenal.

The package offers economic and political rewards if Tehran relinquishes domestic uranium enrichment, which is used to generate power but can also produce weapons-grade uranium for nuclear warheads.

It also contains the implicit threat of U.N. sanctions if Iran remains defiant.

In a breakthrough last week, the United States agreed to join in multinational talks on the package.

Perks, penaltiesDetails of the basket of perks and penalties have not been made public. But an earlier draft shared in part with The Associated Press offered help in building nuclear reactors and a guaranteed supply of fuel as well as an offer to supply European Airbus aircraft for Tehran’s civilian fleet.

Diplomats revealed Monday that Washington has sweetened the offer originally drawn up by France, Britain and Germany by saying it will lift some bilateral sanctions on Tehran such as a ban on Boeing passenger aircraft and related parts if Iran agrees to an enrichment freeze.

One of the diplomats also said Washington would be prepared to take some “dual-use” technology off its banned list of exports to Iran. The term is used for products and material that have military as well as civilian uses. The diplomat declined to go into details.

Iranian officials have sent conflicting signals on the initiative, reflecting a possible struggle within the leadership on how to react. Additionally, the U.S. offer to join in direct talks with Iran might have taken Tehran’s top officials off guard.

Iranian President Mahmoud Ahmadinejad, normally a hardline critic of the United States who insists that Tehran has a right to enrichment, said over the weekend that a breakthrough in negotiations was possible and welcomed the U.S. offer to join talks, while rejecting preconditions.

But threats by Iran’s supreme leader, Ayatollah Ali Khamenei to disrupt the world’s oil supply if Tehran is punished over its nuclear program reflected Tehran’s nervousness.

Although other Iranian officials have repeatedly ruled out using oil as weapon, his comments propelled oil prices to $73 a barrel Monday.

Iran is the world’s fourth-largest oil exporter and the second-largest producer in the Organization of Petroleum Exporting Countries.